netdev - Re: [PATCH net v4] net: bridge: Fix ethernet header pointer before check skb forwardable

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Message-Id: <20190117.215557.221214487674861038.davem@davemloft.net>
Date:   Thu, 17 Jan 2019 21:55:57 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     wangyunjian@...wei.com
Cc:     netdev@...r.kernel.org, xudingke@...wei.com,
        bridge@...ts.linux-foundation.org, nikolay@...ulusnetworks.com,
        roopa@...ulusnetworks.com, stephen@...workplumber.org
Subject: Re: [PATCH net v4] net: bridge: Fix ethernet header pointer before
 check skb forwardable

From: wangyunjian <wangyunjian@...wei.com>
Date: Thu, 17 Jan 2019 09:46:41 +0800

> From: Yunjian Wang <wangyunjian@...wei.com>
> 
> The skb header should be set to ethernet header before using
> is_skb_forwardable. Because the ethernet header length has been
> considered in is_skb_forwardable(including dev->hard_header_len
> length).
> 
> To reproduce the issue:
> 1, add 2 ports on linux bridge br using following commands:
> $ brctl addbr br
> $ brctl addif br eth0
> $ brctl addif br eth1
> 2, the MTU of eth0 and eth1 is 1500
> 3, send a packet(Data 1480, UDP 8, IP 20, Ethernet 14, VLAN 4)
> from eth0 to eth1
> 
> So the expect result is packet larger than 1500 cannot pass through
> eth0 and eth1. But currently, the packet passes through success, it
> means eth1's MTU limit doesn't take effect.
> 
> Fixes: f6367b4660dd ("bridge: use is_skb_forwardable in forward path")
> Cc: bridge@...ts.linux-foundation.org
> Cc: Nkolay Aleksandrov <nikolay@...ulusnetworks.com>
> Cc: Roopa Prabhu <roopa@...ulusnetworks.com>
> Cc: Stephen Hemminger <stephen@...workplumber.org>
> Signed-off-by: Yunjian Wang <wangyunjian@...wei.com>

Applied and queued up for -stable.